IN VIVO ASSESSMENT OF BIOAVAILABILITY OF SUSTAINED RELEASE MATRIX TABLETS OF AN ANTIHYPERTENSIVE DRUG IN RABBITS USING REVERSE PHASE CHROMATOGRAPHY

A new reverse phase high performance liquid chromatographic (RP-HPLC) method was developed and validated for determination of losartan potassium in rabbit plasma. The calibration curve was linear in the concentration range of 0.025 μg/mL to 0.5 μg/mL with a lower limit of detection at 0.025μg/mL. In addition, stability studies of losartan Potassium in rabbit plasma demonstrated its good stability at − 70°C and at room temperature. The validated method was successfully employed for the estimation of losartan potassium in rabbit plasma following oral administrations of immediate release tablets and sustained release matrix tablets to rabbits. The pharmacokinetic parameters including AUC0–t, AUC0–∞, Cmax, Tmax, T1/2, and elimination rate constant (Kel) were determined from plasma concentration for both the formulations. The absorption and bioavailability of drug from the sustained release tablets was found significantly higher as compared to the reference losartan potassium immediate release tablets because of longer half-life and lower elimination.